Boiler safety device



Feb. 27, 1951 P. SPENCE 2,543,558

BOILER SAFETY DEVICE Filed Feb 19, 1946 jfi- 24 22 III! INVENTOR Pawlsezz Spence ATTORNEY 5 Patented Feb. 27, 1951 BOILER SAFETY DEVICE Paulsen Spence, Baton Rouge, La., assignor to Spence Engineering Company, Inc., Walden, N. Y., a corporation of New York Application February 19, 1946, Serial No. 648,770

2 Claims. (01. 122-504) My invention relates to a boiler safety device and in particular to apparatus for terminating the supply of feed water to a boiler when the water in the boiler reaches a predetermined minimuin level.

Power and heating plants are frequently equipped with automatic waterlevel-responsive valving mechanisms for controlling the admission of water to a boiler, with a view to assuring operation at Water levels within predetermined limits. Once in a while, however, these mechanisms develop a defect which may result in the supply of feed water when the boiler has overheated due to attainment of too low a water level. This condition is known to be a frequent cause of boiler explosions.

It is, accordingly, an object of my invention to provide an improved safety device for-reducing the possibility of boiler explosions.

It is also an object to provide a boiler safety device in which feed water to the boiler is automatically cut off upon approach to an unsafe operating condition.

It is another object of the invention to provide means to prevent feed water from entering a boiler when the water falls below a predetermined level, and the boiler is under pressure.

It is a further object to provide a boiler safety device which will require the personal attention of and adjustment by an operator when conditions in the boiler approach an unsafe state.

Other objects and various features of novelty and invention will be hereinafter pointed out or will become apparent to those skilled in the art.

Broadly speaking, my invention in the preferred form includes fluid-level-responsive means for automatically cutting off the fluid supply to a boiler upon attainment of a predetermined mini mum fluid level in the boiler. Human intervention, in the form of a manual operation, is necessary before fluid can again be admitted to the boiler; and, until the pressure within the boiler has abated upon a cooling of the apparatus, means are provided to render this manual operation difiicult if not impossible.

In a specific form to be later described, my invention includes a valve in the feed-water supply line to a boiler. The valve is constantly urged toward a closed position. Manually operable means are provided, however, for opening the valve, and holding means maintain the valve in open position. Water-level-responsive means are associated with the boiler and are efiective to operate the holding means to permit a closing of the valve upon attainment of a dangerously low water 'a predetermined minimum level.

level in the boiler. Since manual operation is required for a reopening of the valve, the operator or foreman responsible for said operation of the boiler is forewarned of the existence of a dangerous condition before additional water can be admitted to the boiler. In a preferred form, my invention includes means responsive to excessive boiler temperatures or pressures for rendering the holding means ineffective for the duration of such unsafe conditions; such an arrangement provides additional insurance that feed water will not be admitted until temperatures and pressures within the boiler have been reduced to safe values.

In the drawings, which show for illustrative purposes only, a preferred form of the invention:

Fig. 1 is a schematic representation of an embodiment of the boiler safety device of my invention;

Fig. 2 is a partial cross-sectional elevation of a valving mechanism which may be employed in the arrangement ofFig. 1;

Fig. 3 is a fragmentary schematic illustration of an alternative arrangement utilizing essentially the same principles as the device of Fig. 1; and

Fig. 4 schematically indicates a further alternative arrangement.

Referring to Fig. 1, a preferred form of my safety device includes a flow-control valve 5 in the feed-water line 6 to a boiler 7. The valve 5 is more completely illustrated in Fig. 2 where it will be seen to include a valve disc 8 arranged to control the flow of water from an inlet port 9, through an outlet port ID, to the water-supply line 6, and thence to the boiler. Disc 8 is constantly urged toward a closed position as by a compression spring H, but a manually operated opening of the valve is possible when a crank or trigger i2 is rotated (clockwise in the sense shown in Fig. 2) to position the control-actuating rod 53,.

associated with disc 8. Means are provided for holding valve 5 open once crank l2 has been manually operated, and in the form shown this means comprises a latch I 4 engaging crank l2 only when in the position shown in Fig. 2. The latch l4 may be steam-pressure operated to release crank l2,

as by displacement of a diaphragm 22 exposed on one side to steam under pressure and, on the other, to atmospheric pressure.

Means are provided to release the holding means l4 when the water in the boiler has reached In the form shown in Fig. 1 thismeans comprises a thermostat 15 which will produce a given physical displacement upon attainment of a preselected limiting temperature. Thermostat I5 is connected to operate a pilot valve 16 in accordance with this displacement, at which time pilot valve I6 becomes effective to supply boiler steam to operate the diaphragm 22 of the latch-releasing mechanism.

Thermostat I5 includes a temperature-responsive element I! in fluid communicable relation with the boiler I over a range of levels including the minimum level below which it is not desired to supply water to the boiler. In the form shown, thermostat element I1 is supported within a fluid-tight envelope I8 having an upper connection 19 and a lower connection 20 to the interior of the boiler. It will be clear that as the boiler level decreases from that shown in Fig. l, greater fractions of the length of thermostat element 57 are exposed to boiler-generated steam, with resultant greater displacement response of the thermostat as a whole. When this displacement has reached the preselected safe limit, the pilot valve l6 will be operated to effect a release of latching means I l-thus cutting off the flow in feed-water line 6.

Preferably, connection IQ is made to the boiler 1 at a level always exposed to steam, so as to prevent convectional circulation of hot water through envelope l8; thus, with steam always overstanding the Water column in envelope [8, the water therein contained will not be subject to active circulation, and will be r latively cool. If desired, the water-level responsiveness of thermostat 15 can be further improved by insertion of cooling means 2| in the line 20 admitting fluid to the lower extremity of envelope l3. This arrangement permits constant maintenance of a relatively large temperature differential in the water-and-steam combination to which thermostat element H may be exposed, so that the thermostat can produce greater physical displacements for a given decrement in water level.

To review, then, the cycle involved in operation of my boiler safety device, the individual responsible for the equipment must first manually open valve 5 by locking crank [2 in its latched position, as shown. Feed water is then admitted to the boiler by manual operation of valves or under the control of other automatic regulating means (not shown) until the boiler is filled to the normal level. If a defect or oversight develops whereby the water in the boiler drops to a dangerously low level, enough of thermostat element I! will be exposed to steam to cause automatic actuation of pilot valve lfi, with resulting release of latch 14 to close valve 5. It will be clear that as long as the boiler remains hot, high pressures will be maintained in the boiler and above diaphragm 22. These pressures are effective to make cooperation of latch M with crank l2 difficult if not impossible, until subsequently obtained reduced pressures reflect cooling to temperatures which will permit the safe admission of feed water.

In the alternative arrangement of Fig. 3 operation is essentially the same as that which has just been described, with the exception that the water-level-responsive means is purely mechanical. In the form shown, a pipe 23 is connected at one end to the diaphragm chamber 24 (containing diaphragm 22) and at the other end to the boiler. The boiler end of pipe 23 is normally sealed off by the disc 25 of a float-controlled valve.

Under the conditions depicted in Fig. 3, the boiler has been filled to a normal water level and it will be understood that, by virtue of the enforced submersion of the float 28, valve disc 25 is positively positioned to cut off Water or any other communication with diaphragm 22 through pipe 23. When the level has dropped to a point at which the float 28 permits the valve 25 to open, pressure fluid from the boiler passes through pipe 23 to the space above diaphragm 22 so as to spring the trigger l4 and cause valve 8 to close as heretofore described. The level at which the float valve 25 is opened is the dangerous low-water level. Again, it will be appreciated that the presence of pressure fluid over diaphragm 22 will keep the latching means ineffective until safely cooled conditions are restored.

In the arrangement according to Fig. 4, a thermostat is employed to actuate an electrically controlled releasing mechanism to close valve 5. The thermostat element ll, the envelope l8 in which it is contained, and the pipes 19 and 20 associating envelope l8 with the side of boiler I will be recognized from the description which has been given above in connection with Fig. 1. Instead of operating a pivot valve, however, the physically displaceable element 29 of thermostat IE is arranged to break an electric circuit when the lower limiting safe water level has been reached. The electric circuit includes a power supply energizing an electromagnet 30, in series connection with a switch which is operated by the displaceable element 29 of the thermostat. In the form shown, the switch comprises a contact arm 3! normally engaging a contact 32 to complete the electric circuitthus energizing the coils of magnet 30. When energized, magnet 30 may support a core element 33 in raised position against the downward force supplied by the action of gravity and of means such as a spring 34. By means of a system of linkages 35 associating the magnet core 33 with the latch member l4 it is clear that crank l2 of the valve 5 will be positively released (and valve 5 therefore positively closed) whenever the electric circuit is interrupted-and this occurs at least when the water level drops below the safe lower limit. Subsequent accidental or other premature closure of the electric circuit, whereas it might result in actuation of latch M, will clearly not have the effect of opening valve 5 or of holding valve 5 open, unless crank l2 has first been manually operated. Furthermore, magnet 30 will not be effective to hold valve 5 open, until the electrical contacts 3I-32 of thermostat l5 have closed to reflect a safely cooled condition within the boiler.

It will be seen that I have provided improved means for reducing the possibility of boiler explosions. This improved means is inherently automatic in cutting off the supply of feed water to a boiler upon approach to unsafe operating conditions. The improvement has the further feature of making difficult, if not impossible, the further supply of feed water if conditions continue to be unsafe. Thus, I provide for utmost safety even under conditions of human carelessness.

While the invention has been described in considerable detail, and a preferred form illustrated, it is to be understood that various changes and modifications may be made within the inventive scope defined in the appended claims.

I claim:

1. In a safety device for a boile having a feedwater supply, an automatic safety shut-off valve in said feed-water supply, said valve including latch means to hold said valve open, said latch means including pressure-responsive means responsive to boiler-steam pressure to hold open said latch means as long as said pressure-responsive means is subjected to boiler-steam pressure, whereby said valve cannot be held open as long as said latch means is subjected to boilersteam pressure, pilot-valve means for controlling admission of steam to said pressure-responsive means, and low-Water-level-responsive actuating means for said pilot-valve means, said pilot-valve means being closed when the boiler water is above a given low level and openable when the boiler Water is below such level, whereby regardless .of boiler-water level, feed water may be admitted only as long as temperature and pressure conditions are safe at the given low level.

2. In a safety device for a boiler having a feedwater supply, an automatic safety shut-off valve in said feed-Water supply to shut off said feedwater supply at a given low level, said valve including latch means to hold said valve open, said latch means including pressure-responsive means to hold open said latch means in response to a given actuating pressure, whereby said valve cannot be held open as long as said latch means is pressure-actuated, pilot means for controlling pressure applied to said pressure-responsive means, and thermostatic means for actuating said pilot means, said thermostatic means being disposed to respond to attainment of a predetermined temperature at a given low-water level in the boiler, said thermostatic means being effective to enable said pilot means to control an application of pressure to said pressure-responsive means upon detection of a, given temperature at said given low-water level, said thermostatic means being further effective to prevent said pilot means from applying pressure to said pressureresponsive means upon detection of temperatures less than said given temperature, whereby regardless of boiler-Water level, feed water may be admitted only as long as temperature and pressure conditions are safe at the given low level.

PAULSEN SPENCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 400,920 Krouse Apr. 9, 1889 677,182 Dean June 25, 1901 895,342 Collin Aug. 4, 1908 993,628 Williams May 30, 1911 1,288,149 Ofeldt Dec. 17, 1918 1,496,990 Kunitz June 10, 1924 1,654,679 Coddington Jan. 3, 1928 1,706,942 Smith Mar. 26, 1929 1,717,394 Ludeman June 18, 1929 1,877,349 Mears Sept. 13, 1932 2,098,912 Dillman Nov. 9, 1937 2,426,909 Waterman Sept. 2, 1947 

